Bottled wine often has tartar precipitates in the form of crystals on the bottom of the bottle. Such precipitates occur between bottling and consumption. These precipitates make the product unattractive to consumers.
Various methods have been proposed for preventing tartar precipitates. Tartar precipitates have been removed by cooling, cation exchange, anion exchange, reverse osmosis, and electrodialysis. Also, tartar precipitates have been inhibited by the use of additives.
Of the above methods, the cooling methods have been commonly used. The other methods have not been used commercially, since they suffer from various disadvantages.
A cooling method based on the primary nucleation of potassium hydrogentartrate, which is a major component of tartar, is known. However, this method requires the maintenance of supersaturated solutions for a long time to produce natural nucleation. Thus, if cannot serve market demand immediately, and it requires a large initial investment for cooling equipment and storage equipment.
Another cooling method is known which comprises increasing tartar concentration by freezing and thickening wine to accelerate nucleation. However, this method cannot steadily crystallize and remove tartar and requires additional freezing equipment. This still further increases initial equipment costs.
To accelerate natural crystal growth, some cooling methods have been proposed that comprise growing tartar crystals by adding tartar seed crystals to the source liquid of wine, and thereafter separating the tartar crystals. These seeding methods are divided into two categories: A first contact method and a second carrier adhesion method. The first method is disclosed, for example, in West German Patent DE No. 3244221Cl issued to Westfaria Co. This publication discloses a process in which seed crystals of potassium hydrogentartrate and dipotassium DL-tartrate are added to precipitate and remove calcium ions which inhibit the growth of tartar crystals. In Japanese Examined Patent Publication No. 39157/1982, issued to Henkel and Co., a process is disclosed in which calcium carbonate is employed as the seed crystal material. The second method is disclosed, for example, in Japanese Examined Patent Publication No. 5157/1981, issued to Henkel and Co. This publication discloses a process in which tartar is extracted from wine through the adhesion of the tartar on carriers made of fiber, etc. The carriers carry the tartar crystals to promote the extraction.
Draft tube baffled crystallizers (hereinafter referred to as DTB crystallizers) have been used in general crystallization processes. A typical DTB crystallizer is illustrated in FIG. 3. In FIG. 3, the numeral 1 identifies a DTB crystallizer equipped with a draft tube 2 centered in the lower half of the DTB crystallizer 1. A propeller 3 is mounted at the bottom of the draft tube 2. The propeller 3 is driven by a motor M connected to the propeller 3 via a shaft. An interposed tube 8 surrounds the draft tube 2, and a vessel 9 surrounds the interposed tube 8. Rotation of the propeller 3 forces an upward flow of liquid introduced from an inlet 4 into the draft tube 2, downward flow of the liquid between the interposed tube 8 and the draft tube 2, and upward flow of the liquid toward an outlet 7 between the interposed tube 8 and the vessel 9.
The numeral 5 identifies a classification leg for separation. Crystals grow inside the draft tube 2 and between the draft tube 2 and the interposed tube 8. These two volumes form a crystallization zone. A space 6 between the interposed tube 8 and the vessel 9 forms a fine trap zone F from which fine crystals on the upward flow are discharged through the outlet 7. Crystals which have grown to some extent remain in the crystallization zone and are allowed to grow uniformly and larger. It is to be understood that the feature of the DTB crystallizer resides in that the interposed tube 8, which extends inside the crystallization zone, functions as a baffle, facilitating the separation of fine crystals from grown crystals. A cooling jacket J to which coolant is supplied is provided on the vessel 9.
As stated above, some of the salient disadvantages of the known cooling methods are that they require expensive equipment for cooling, storage, and concentration; that they do not operate steadily; and that they take a long time to accomplish detartarification because they are based on natural nucleation.
The methods based on cation exchange, anion exchange, reverse osmosis, electrodialysis, or inhibitors also suffer from salient disadvantages that prevent their use on an industrial scale. Even in the field of the seeding method (which is pertinent to the present invention), there are problems due to the requirement to add additives to precipitate calcium ions, which inhibit tartar crystallization (as in the above German Patent), due to the requirement for supply carriers to promote contact between seed and liquid.
To solve the above disadvantages, the application of DTB crystallizers was examined. However, conventional DTB crystallizers are not suitable to tartar crystallization of wine or grape juice, since the concept of the draft and the classification for such crystals is different from that of other fields. In addition, conventional DTB crystallizers are expensive due to their complicated structure. Furthermore, the complicated structures make it difficult to clean the inside of the crystallizers in place, which is not favorable from the viewpoint of sanitation.